U.S. patent number 10,676,550 [Application Number 15/742,552] was granted by the patent office on 2020-06-09 for copolymers and films thereof.
This patent grant is currently assigned to INEOS EUROPE AG. The grantee listed for this patent is INEOS EUROPE AG. Invention is credited to Serge Desportes, Imen Ghouila, Claudine Lalanne-Magne, Eric Osmont.
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United States Patent |
10,676,550 |
Desportes , et al. |
June 9, 2020 |
Copolymers and films thereof
Abstract
Novel copolymers having a density (D) in the range 0.895-0.910
g/cm.sup.3, a melt index MI.sub.2 (2.16 kg, 190.degree. C.) in the
range of 0.01-6 g/10 min, a Compositional Distribution Branch Index
(CDBI) in the range 55-85%, and a sealing initiation temperature
(SIT) and density (D) satisfying the relationship
SIT.ltoreq.(A.times.D)-B wherein A is 800.degree.
C..times.cm.sup.3/g and B is 650.degree. C., wherein the SIT
(.degree. C.) is determined on a 70 .mu.m film at 0.5N/15 mm and D
Is in units of g/cm.sup.3 are disclosed. The copolymers may be
suitably prepared by use of metallocene catalyst systems and may be
used in film applications, in particular as sealing layers for
packaging applications.
Inventors: |
Desportes; Serge
(Simiane-Collongue, FR), Ghouila; Imen (Martigues,
FR), Lalanne-Magne; Claudine (Saint Mitre les
Remparts, FR), Osmont; Eric (Martigues,
FR) |
Applicant: |
Name |
City |
State |
Country |
Type |
INEOS EUROPE AG |
Vaud |
N/A |
CH |
|
|
Assignee: |
INEOS EUROPE AG (Vaud,
CH)
|
Family
ID: |
53773211 |
Appl.
No.: |
15/742,552 |
Filed: |
July 7, 2016 |
PCT
Filed: |
July 07, 2016 |
PCT No.: |
PCT/EP2016/066166 |
371(c)(1),(2),(4) Date: |
January 08, 2018 |
PCT
Pub. No.: |
WO2017/005867 |
PCT
Pub. Date: |
January 12, 2017 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20180201705 A1 |
Jul 19, 2018 |
|
Foreign Application Priority Data
|
|
|
|
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Jul 9, 2015 [EP] |
|
|
15176047 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C08J
5/18 (20130101); C08F 210/16 (20130101); C08F
210/16 (20130101); C08F 4/6592 (20130101); C08F
210/16 (20130101); C08F 2/34 (20130101); C08F
210/16 (20130101); C08F 210/14 (20130101); C08F
2500/06 (20130101); C08F 2500/12 (20130101); C08F
2500/08 (20130101); C08F 4/65916 (20130101); C08F
4/65912 (20130101); C08F 2420/02 (20130101); C08F
2410/01 (20130101); C08F 4/65908 (20130101); C08J
2323/08 (20130101) |
Current International
Class: |
C08F
210/16 (20060101); C08F 4/6592 (20060101); C08J
5/18 (20060101); C08F 4/659 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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|
|
|
|
0 608 369 |
|
May 1997 |
|
EP |
|
1 325 073 |
|
May 2007 |
|
EP |
|
WO 94/14855 |
|
Jul 1994 |
|
WO |
|
WO 94/26816 |
|
Nov 1994 |
|
WO |
|
WO 96/08521 |
|
Mar 1996 |
|
WO |
|
WO 2006/085051 |
|
Aug 2006 |
|
WO |
|
WO 2008/074689 |
|
Jun 2008 |
|
WO |
|
Other References
International Search Report for PCT/EP2016/066166, dated Oct. 7,
2016, 4 pages. cited by applicant .
Written Opinion of the ISA for PCT/EP2016/066166, dated Oct. 7,
2016, 6 pages. cited by applicant .
Fisher, "Advanced Sclairtech--A New Approach to Easy Processing
Single Site Resins", Processing Metallocene Polyolefins, Oct.
19-20, 1999, 9 pages. cited by applicant .
McAuley et al., On-Line Inference of Polymer Properties in an
Industrial Polyethylene Reactor, AIChe Journal, vol. 37, No. 6, pp.
825-835, (Jun. 1991). cited by third party.
|
Primary Examiner: Lu; Caixia
Attorney, Agent or Firm: Nixon & Vanderhye P.C.
Claims
The invention claimed is:
1. A copolymer of ethylene and an alpha-olefin, said copolymer
having (a) a density (D) in the range 0.895-0.910 g/cm.sup.3, (b) a
melt index MI.sub.2 (2.16 kg, 190.degree. C.) in the range of
0.01-6 g/10 min, (c) a Compositional Distribution Branch Index
(CDBI) in the range 55-85%, and (d) a sealing initiation
temperature (SIT) and density (D) satisfying the relationship
SIT.ltoreq.(A.times.D)-B wherein A is 1700.degree.
C..times.cm.sup.3/g and B is 1469.degree. C., and wherein the SIT
(.degree. C.) is determined on a 70 .mu.m film at 0.5N/15 mm and D
is in units of g/cm.sup.3, and (e) a Crystallizable Species
Fraction below 55.degree. C. (CSF55).gtoreq.12%.
2. A copolymer according to claim 1 having a Compositional
Distribution Branch Index (CDBI) in the range 65-85%.
3. A copolymer according to claim 1 having a density in the range
0.901-0.907 g/cm.sup.3.
4. A copolymer according to claim 1 having a melt index MI.sub.2
(2.16 kg, 190.degree. C.) in the range of 0.05-5 g/10 min.
5. A copolymer according to claim 1 having a sealing initiation
temperature (SIT)<72.degree. C.
6. A copolymer according to claim 1 having a molecular weight
distribution (Mw/Mn) greater than 3.4 and less than 4.5.
7. A copolymer according to claim 1 wherein the alpha-olefin is
1-hexene.
8. A copolymer according to claim 1 prepared in the presence a
metallocene catalyst system.
9. A copolymer according to claim 8 wherein the metallocene
catalyst system comprises a monocyclopentadienyl metallocene
complex.
10. A copolymer according to claim 1 exhibiting a powder
compressability (C) as follows: % C<(-A'.times.D)+B' wherein D
is the density in kg/m.sup.3 and A'=1 and B'=928.
11. A copolymer according to claim 1 exhibiting a powder
compressability (C) as follows: % C<(-A.times.D)+B' wherein D is
the density in kg/m.sup.3 and wherein A'=0.5 and B'=468.
12. A copolymer according to claim 1 having a Compositional
Distribution Branch Index (CDBI) in the range 65-85%.
13. A copolymer according to claim 1 having a sealing initiation
temperature (SIT)<65.degree. C.
14. A copolymer according to claim 1 having a Crystallizable
Species Fraction below 55.degree. C. (CSF55).gtoreq.15%.
Description
This application is the U.S. national phase of International
Application No. PCT/EP2016/066166 filed Jul. 7, 2016 which
designated the U.S. and claims priority to EP Patent Application
No. 15176047.7 filed Jul. 9, 2015, the entire contents of each of
which are hereby incorporated by reference.
The present invention relates to novel copolymers and in particular
to novel copolymers of ethylene and alpha-olefins in particular to
linear low density polyethylenes (LLDPE) and also to films produced
from said copolymers.
In recent years there have been many advances in the production of
polyolefin copolymers due to the introduction of metallocene
catalysts. Metallocene catalysts offer the advantage of generally
higher activity than traditional Ziegler catalysts and are usually
described as catalysts which are single-site in nature. Because of
their single-site nature the polyolefin copolymers produced by
metallocene catalysts often are quite uniform in their molecular
structure. For example, in comparison to traditional Ziegler
produced materials, they have relatively narrow molecular weight
distributions and narrow Short Chain Branching Distribution
(SCBD).
Although certain properties of metallocene products are enhanced by
narrow molecular weight distribution, difficulties are often
encountered in the processing of these materials into useful
articles and films relative to Ziegler produced materials. In
addition, the uniform nature of the SCBD of metallocene produced
materials does not readily permit certain structures to be
obtained.
Recently a number of patents have published directed to the
preparation of films based on low density polyethylenes prepared
using metallocene catalyst compositions.
EP 608369 describes copolymers having a melt flow ratio
(I.sub.10/I.sub.2) of .gtoreq.5.63 and a molecular weight
distribution (Mw/Mn) satisfying the relationship
Mw/Mn.ltoreq.(I.sub.10/I.sub.2)-4.63. The copolymers are described
as elastic substantially linear olefin polymers having improved
processability and having between 0.01 to 3 long chain branches per
1000 C atoms and show the unique characteristic wherein the
I.sub.10/I.sub.2 is essentially independent of Mw/Mn.
WO 94/14855 discloses linear low density polyethylene (LLDPE) films
prepared using a metallocene, alumoxane and a carrier. The
metallocene component is typically a bis (cyclopentadienyl)
zirconium complex exemplified by bis (n-butylcyclopentadienyl)
zirconium dichloride and is used together with methyl alumoxane
supported on silica. The LLDPE's are described in the patent as
having a narrow Mw/Mn of 2.5-3.0, a melt flow ratio (MFR) of 15-25
and low zirconium residues.
WO 94/26816 also discloses films prepared from ethylene copolymers
having a narrow composition distribution. The copolymers are also
prepared from traditional metallocenes (eg bis (1-methyl,
3-n-butylcyclopentadienyl) zirconium dichloride and methylalumoxane
deposited on silica) and are also characterised in the patent as
having a narrow Mw/Mn values typically in the range 3-4 and in
addition by a value of Mz/Mw of less than 2.0.
Our application WO 2006/085051 describes copolymers prepared by use
of supported monocyclopentadienyl metallocene complexes activated
by borates suitable for use in film applications. The copolymers
have broader molecular weight distributions (3.5 to 4.5) and low or
moderate amounts of long chain branching (LCB) and are advantageous
for producing films having an excellent balance of processing,
optical and mechanical properties. Exemplified copolymers are those
with density of 0.918/0.919 g/cm.sup.3 and melt index (MI.sub.2) of
0.95 to 1.3.
WO 2008/074689 describes similar copolymers prepared from the same
supported catalyst systems but with a more balanced processability.
The copolymers are characterised by the relationship between the
Dow Rheology Index (DRI), melt elastic modulus and melt index and
again the copolymers are exemplified with densities of 0.918-0.921
g/cm.sup.3 and melt indices (MI.sub.2) in the range 1.1 to 1.3. The
copolymers are also advantageous for producing films having an
excellent balance of processing, optical and mechanical
properties.
Polyethylenes are widely used for flexible packaging applications
due to their ability to form seals at low temperature. The lower
the temperature the faster the seal is formed and the packaging
line may therefore be run faster resulting in overall reduced
conversion costs. An important parameter for selecting a suitable
polymer is therefore the sealing initiation temperature (SIT) of
the polymer selected as the sealing layer in the packaging.
The sealing initiation temperature (SIT), typically determined for
example at 0.5N/15 mm, is defined as the minimum sealing
temperature required to form a seal with a strength above 0.5N for
a film specimen of 15 mm width. As the sealing process is mainly
governed by the melting and diffusion of the sealing layers, the
lower the crystallinity, which is determined by density, then the
lower the SIT.
Traditionally polymers with density in the range 0.920-0.925
g/cm.sup.3 have been preferred for this application having a SIT
ranging between 104 to 115.degree. C. Linear low density
polyethylenes (LLDPE) prepared using metallocene catalyst systems
typically have a SIT in the range 95-100.degree. C. Ultra low or
very low density polyethylenes (VLDPEs) may have a SIT as low as
about 72.degree. C.
WO 96/08521 describes metallocene-catalysed gas phase
polymerization process producing polymers having very low densities
in the range 0.85-0.89 g/cc and a Composition Distribution
Branching Index (CDBI)>60%. The metallocenes are unbridged
bis(cyclopentadienyl) metallocene complexes. The polymers are
suitable for film applications but no details of film properties
are reported.
EP 1325073 describes metallocene-produced very low density
polyethylenes (VLDPE) having densities in the range 0.905-0.915
g/cm.sup.3 and CDBI in the range 55-70% by weight. The VLDPEs are
prepared in the gas phase also using unbridged
bis(cyclopentadienyl) metallocene complexes and have a relatively
narrow molecular weight distribution as expressed by a Mw/Mn in the
range 2-3 and a Mz/Mw less than 2. The polymers are suitable for
film applications reporting improved hot tack strength at low
initiation temperatures.
An article in Processing Metallocene Polyolefins Paper 13, 1 Jan.
1999, Pgs 1-8 compares the processabilities and sealing performance
of films derived from resins prepared from single site catalyst
systems. SITs of between 64.degree. C. and 73.degree. C. are
reported for resins having densities .ltoreq.0.910 g/cm.sup.3.
We have now developed novel linear low density polymers having a
SIT below 72.degree. C. using supported monocyclopentadienyl
metallocene systems as described in the aforementioned WO
2006/085051 and WO 2008/074689. The novel copolymers are preferably
produced in the gas phase.
Surprisingly said copolymers exhibit an unexpected relationship
between density and SIT at lower densities and may advantageously
be used as sealing layers for packaging applications.
In addition the novel copolymers of the present invention exhibit
CDBIs in the range 55-85% typical of resins based on metallocene
catalyst systems but much higher than that observed with
traditional Ziegler Natta catalyst systems or resins produced by
single site catalysts performed in the solution phase thereby
providing the advantages of lower SITs but with improved
processability.
Thus according to a first aspect of the present invention there is
provided a copolymer of ethylene and an alpha-olefin, said
copolymer having (a) a density (D) in the range 0.895-0.910
g/cm.sup.3, (b) a melt index MI.sub.2 (2.16 kg, 190.degree. C.) in
the range of 0.01-6 g/10 min, (c) a Compositional Distribution
Branch Index (CDBI) in the range 55-85%, and (d) a sealing
initiation temperature (SIT) and density (D) satisfying the
relationship SIT.ltoreq.(A.times.D)-B wherein A is 800.degree.
C..times.cm.sup.3/g and B is 650.degree. C. wherein the SIT
(.degree. C.) is determined on a 70 .mu.m film at 0.5N/15 mm and D
is in units of g/cm.sup.3.
The copolymers of the present invention exhibit a CDBI preferably
in the range 65-85%.
The preferred relationship between the sealing initiation
temperature (SIT) and density (D) is when A is 1200.degree.
C..times.cm.sup.3/g and B is 1014.degree. C. and most preferred
when A is 1700.degree. C..times.cm.sup.3/g and B is 1469.degree.
C.
Preferred copolymers have a density (D) in the range 0.900 to 0.910
g/cm.sup.3, and most preferably in the range 0.901 to 0.907
g/cm.sup.3.
Preferred copolymers have a melt index in the range 0.05 to 5 g/10
min and most preferably in the range 1.2 to 1.6 g/10 min.
The copolymers preferably have a sealing initiation temperature
(SIT) at 0.5N on a 15 mm film of <72.degree. C.
The preferred SIT is <70.degree. C. and most preferably
<65.degree. C.
The copolymers exhibit a Crystallizable Species Fraction below
55.degree. C. (CSF55).gtoreq.12% and preferably .gtoreq.15%.
The copolymers of the present invention have a molecular weight
distribution (Mw/Mn) greater than 3 and less than 5, preferably
greater than 3.2 and less than 4.5 and most preferably greater than
3.4 and less than 4.5.
The copolymers of the present invention also have a value for Mz/Mn
in the range 2.0 to 4.0, preferably in the range 2.2 to 3.5 and
most preferably in the range 2.32 to 3.0.
Preferred alpha-olefins are those having C4-C12 carbon atoms. Most
preferred alpha-olefins are 1-butene, 1-hexene, 4-methyl-1-pentene
and 1-octene.
The preferred alpha-olefin is 1-hexene.
The novel copolymers of the present invention may suitably be
prepared by use of a metallocene catalyst system comprising,
preferably a monocylcopentadienyl metallocene complex having a
`constrained geometry` configuration together with a suitable
activator.
Examples of monocyclopentadienyl or substituted
monocyclopentadienyl complexes suitable for use in the present
invention are described in EP 416815, EP 418044. EP 420436 and EP
551277.
Suitable complexes may be represented by the general formula:
CpMX.sub.n
wherein Cp is a single cyclopentadienyl or substituted
cyclopentadienyl group optionally covalently bonded to M through a
substituent, M is a Group VIA metal bound in a .eta..sup.5 bonding
mode to the cyclopentadienyl or substituted cyclopentadienyl group.
X each occurrence is hydride or a moiety selected from the group
consisting of halo, alkyl, aryl, aryloxy, alkoxy, alkoxyalkyl,
amidoalkyl, siloxyalkyl etc. having up to 20 non-hydrogen atoms and
neutral Lewis base ligands having up to 20 non-hydrogen atoms or
optionally one X together with Cp forms a metallocycle with M and n
is dependent upon the valency of the metal.
Preferred monocyclopentadienyl complexes have the formula:
##STR00001##
wherein:--
R' each occurrence is independently selected from hydrogen,
hydrocarbyl, silyl, germyl, halo, cyano, and combinations thereof,
said R' having up to 20 nonhydrogen atoms, and optionally, two R'
groups (where R' is not hydrogen, halo or cyano) together form a
divalent derivative thereof connected to adjacent positions of the
cyclopentadienyl ring to form a fused ring structure;
X is hydride or a moiety selected from the group consisting of
halo, alkyl, aryl, aryloxy, alkoxy, alkoxyalkyl, amidoalkyl,
siloxyalkyl etc. having up to 20 non-hydrogen atoms and neutral
Lewis base ligands having up to 20 non-hydrogen atoms, Y is --O--,
--S--, --NR*--, --PR*--, M is hafnium, titanium or zirconium, Z* is
SiR*.sub.2, CR*.sub.2, SiR*.sub.2SIR*.sub.2, CR*.sub.2CR*.sub.2,
CR*.dbd.CR*, CR*.sub.2SiR*.sub.2, or
GeR*2, wherein:
R* each occurrence is independently hydrogen, or a member selected
from hydrocarbyl, silyl, halogenated alkyl, halogenated aryl, and
combinations thereof, said
R* having up to 10 non-hydrogen atoms, and optionally, two R*
groups from Z* (when R* is not hydrogen), or an R* group from Z*
and an R* group from Y form a ring system,
and n is 1 or 2 depending on the valence of M.
Examples of suitable monocyclopentadienyl complexes are
(tert-butylamido) dimethyl
(tetramethyl-.eta..sup.5-cyclopentadienyl) silanetitanium
dichloride and (2-methoxyphenylamido) dimethyl
(tetramethyl-.eta..sup.5-cyclopentadienyl) silanetitanium
dichloride.
Particularly preferred metallocene complexes for use in the
preparation of the copolymers of the present invention may be
represented by the general formula:
##STR00002##
wherein:--
R' each occurrence is independently selected from hydrogen,
hydrocarbyl, silyl, germyl, halo, cyano, and combinations thereof,
said R' having up to 20 nonhydrogen atoms, and optionally, two R'
groups (where R' is not hydrogen, halo or cyano) together form a
divalent derivative thereof connected to adjacent positions of the
cyclopentadienyl ring to form a fused ring structure;
X is a neutral .eta..sup.4 bonded diene group having up to 30
non-hydrogen atoms, which forms a in-complex with M;
Y is --O--, --S--, --NR*--, --PR*--,
M is titanium or zirconium in the +2 formal oxidation state;
Z* is SiR*.sub.2, CR*.sub.2, SiR*.sub.2SIR*.sub.2,
CR*.sub.2CR*.sub.2, CR*.dbd.CR*, CR*.sub.2SiR*.sub.2, or
GeR*.sub.2, wherein:
R* each occurrence is independently hydrogen, or a member selected
from hydrocarbyl, silyl, halogenated alkyl, halogenated aryl, and
combinations thereof, said
R* having up to 10 non-hydrogen atoms, and optionally, two R*
groups from Z* (when R* is not hydrogen), or an R* group from Z*
and an R* group from Y form a ring system.
Examples of suitable X groups include
s-trans-.eta..sup.4-1,4-diphenyl-1,3-butadiene,
s-trans-.eta..sup.4-3-methyl-1,3-pentadiene;
s-trans-.eta..sup.4-2,4-hexadiene;
s-trans-.eta..sup.4-1,3-pentadiene;
s-trans-.eta..sup.4-1,4-ditolyl-1,3-butadiene;
s-trans-.eta..sup.4-1,4-bis(trimethylsilyl)-1,3-butadiene;
s-cis-.eta..sup.4-3-methyl-1,3-pentadiene;
s-cis-.eta..sup.4-1,4-dibenzyl-1,3-butadiene;
s-cis-.eta..sup.4-1,3-pentadiene;
s-cis-.eta..sup.4-1,4-bis(trimethylsilyl)-1,3-butadiene, said s-cis
diene group forming a .pi.-complex as defined herein with the
metal.
Most preferably R' is hydrogen, methyl, ethyl, propyl, butyl,
pentyl, hexyl, benzyl, or phenyl or 2 R' groups (except hydrogen)
are linked together, the entire C.sub.5R'.sub.4 group thereby
being, for example, an indenyl, tetrahydroindenyl, fluorenyl,
terahydrofluorenyl, or octahydrofluorenyl group.
Highly preferred Y groups are nitrogen or phosphorus containing
groups containing a group corresponding to the formula
--N(R.sup.//)-- or --P(R.sup.//)-- wherein R.sup.// is C.sub.1-10
hydrocarbyl.
Most preferred complexes are amidosilane--or amidoalkanediyl
complexes.
Most preferred complexes are those wherein M is titanium.
Specific complexes are those disclosed in WO 95/00526 and are
incorporated herein by reference.
A particularly preferred complex is (t-butylamido)
(tetramethyl-.eta..sup.5-cyclopentadienyl) dimethyl
silanetitanium-.eta..sup.4-1,3-pentadiene.
Suitable cocatalysts for use in the preparation of the novel
copolymers of the present invention are those typically used with
the aforementioned metallocene complexes.
These include aluminoxanes such as methyl aluminoxane (MAO),
boranes such as tris(pentafluorophenyl) borane and borates.
Aluminoxanes are well known in the art and preferably comprise
oligomeric linear and/or cyclic alkyl aluminoxanes. Aluminoxanes
may be prepared in a number of ways and preferably are prepare by
contacting water and a trialkylaluminium compound, for example
trimethylaluminium, in a suitable organic medium such as benzene or
an aliphatic hydrocarbon.
A preferred aluminoxane is methyl aluminoxane (MAO).
Other suitable cocatalysts are organoboron compounds in particular
triarylboron compounds. A particularly preferred triarylboron
compound is tris(pentafluorophenyl) borane.
Other compounds suitable as cocatalysts are compounds which
comprise a cation and an anion. The cation is typically a Bronsted
acid capable of donating a proton and the anion is typically a
compatible non-coordinating bulky species capable of stabilizing
the cation.
Such cocatalysts may be represented by the formula:
(L*-H).sup.+.sub.d(A.sup.d-)
wherein:--
L* is a neutral Lewis base
(L*-H).sup.+.sub.d is a Bronsted acid
A.sup.d- is a non-coordinating compatible anion having a charge of
d.sup.-, and
d is an integer from 1 to 3.
The cation of the ionic compound may be selected from the group
consisting of acidic cations, carbonium cations, silylium cations,
oxonium cations, organometallic cations and cationic oxidizing
agents.
Suitably preferred cations include trihydrocarbyl substituted
ammonium cations eg, triethylammonium, tripropylammonium,
tri(n-butyl)ammonium and similar. Also suitable are
N,N-dialkylanilinium cations such as N,N-dimethylanilinium
cations.
The preferred ionic compounds used as cocatalysts are those wherein
the cation of the ionic compound comprises a hydrocarbyl
substituted ammonium salt and the anion comprises an aryl
substituted borate.
Typical borates suitable as ionic compounds include:
triethylammonium tetraphenylborate triethylammonium
tetraphenylborate, tripropylammonium tetraphenylborate,
tri(n-butyl)ammonium tetraphenylborate, tri(t-butyl)ammonium
tetraphenylborate, N,N-dimethylanilinium tetraphenylborate,
N,N-diethylanilinium tetraphenylborate, trimethylammonium
tetrakis(pentafluorophenyl) borate, triethylammonium
tetrakis(pentafluorophenyl) borate, tripropylammonium
tetrakis(pentafluorophenyl) borate, tri(n-butyl)ammonium
tetrakis(pentafluorophenyl) borate, N,N-dimethylanilinium
tetrakis(pentafluorophenyl) borate, N,N-diethylanilinium
tetrakis(pentafluorophenyl) borate.
A preferred type of cocatalyst suitable for use with the
metallocene complexes comprise ionic compounds comprising a cation
and an anion wherein the anion has at least one substituent
comprising a moiety having an active hydrogen.
Suitable cocatalysts of this type are described in WO 98/27119 the
relevant portions of which are incorporated herein by
reference.
Examples of this type of anion include: triphenyl(hydroxyphenyl)
borate tri (p-tolyl)(hydroxyphenyl) borate tris
(pentafluorophenyl)(hydroxyphenyl) borate tris
(pentafluorophenyl)(4-hydroxyphenyl) borate
Examples of suitable cations for this type of cocatalyst include
triethylammonium, triisopropylammonium, diethylmethylammonium,
dibutylethylammonium and similar.
Particularly suitable are those cations having longer alkyl chains
such as dihexyldecylmethylammonium, dioctadecylmethylammonium,
ditetradecylmethylammonium, bis(hydrogentated tallow alkyl)
methylammonium and similar.
Particular preferred cocatalysts of this type are alkylammonium
tris(pentafluorophenyl) 4-(hydroxyphenyl) borates. A particularly
preferred cocatalyst is bis(hydrogenated tallow alkyl) methyl
ammonium tris (pentafluorophenyl) (4-hydroxyphenyl) borate.
With respect to this type of cocatalyst, a preferred compound is
the reaction product of an alkylammonium
tris(pentaflurophenyl)-4-(hydroxyphenyl) borate and an
organometallic compound, for example triethylaluminium or an
aluminoxane such as tetraisobutylaluminoxane.
The catalysts used to prepare the novel copolymers of the present
invention may suitably be supported.
Suitable support materials include inorganic metal oxides or
alternatively polymeric supports may be used for example
polyethylene, polypropylene, clays, zeolites, etc.
The most preferred support material for use with the supported
catalysts according to the method of the present invention is
silica. Suitable silicas include Ineos ES70 and Grace Davison 948
silicas.
The support material may be subjected to a heat treatment and/or
chemical treatment to reduce the water content or the hydroxyl
content of the support material. Typically chemical dehydration
agents are reactive metal hydrides, aluminium alkyls and halides.
Prior to its use the support material may be subjected to treatment
at 100.degree. C. to 1000.degree. C. and preferably at 200 to
850.degree. C. in an inert atmosphere under reduced pressure.
The porous supports are preferably pretreated with an
organometallic compound preferably an organoaluminium compound and
most preferably a trialkylaluminium compound in a dilute
solvent.
The support material is pretreated with the organometallic compound
at a temperature of -20.degree. C. to 150.degree. C. and preferably
at 20.degree. C. to 100.degree. C.
Particularly suitable catalysts for use in the preparation of the
copolymers of the present invention are metallocene complexes which
have been treated with polymerisable monomers. Our earlier
applications WO 04/020487 and WO 05/019275 describe supported
catalyst compositions wherein a polymerisable monomer is used in
the catalyst preparation.
Polymerisable monomers suitable for use in this aspect of the
present invention include ethylene, propylene, 1-butene, 1-hexene,
I-octene, 1-decene, styrene, butadiene, and polar monomers for
example vinyl acetate, methyl methacrylate, etc. Preferred monomers
are those having 2 to 10 carbon atoms in particular ethylene,
propylene, 1-butene or 1-hexene.
Alternatively a combination of one or more monomers may be used for
example ethylene and 1-hexene.
The preferred polymerisable monomer is 1-hexene.
The polymerisable monomer is suitably used in liquid form or
alternatively may be used in a suitable solvent. Suitable solvents
include for example heptane.
The polymerisable monomer may be added to the cocatalyst before
addition of the metallocene complex or alternatively the complex
may be pretreated with the polymerisable monomer.
The novel copolymers of the present invention may suitably be
prepared in processes performed in either the slurry or the gas
phase.
A slurry process typically uses an inert hydrocarbon diluent and
temperatures from about 0.degree. C. up to a temperature just below
the temperature at which the resulting polymer becomes
substantially soluble in the inert polymerisation medium. Suitable
diluents include toluene or alkanes such as hexane, propane or
isobutane. Preferred temperatures are from about 30.degree. C. up
to about 200.degree. C. but preferably from about 60.degree. C. to
100.degree. C. Loop reactors are widely used in slurry
polymerisation processes.
The novel copolymers are most suitably prepared in a gas phase
process.
Gas phase processes for the polymerisation of olefins, especially
for the homopolymerisation and the copolymerisation of ethylene and
.alpha.-olefins for example 1-butene, 1-hexene, 4-methyl-1-pentene
are well known in the art.
Typical operating conditions for the gas phase are from 20.degree.
C. to 100.degree. C. and most preferably from 40.degree. C. to
85.degree. C. with pressures from subatmospheric to 100 bar.
Preferred gas phase processes are those operating in a fluidised
bed. Particularly preferred gas phase processes are those operating
in "condensed mode" as described in EP 89691 and EP 699213 the
latter being a particularly preferred process.
By "condensed mode" is meant the "process of purposefully
introducing a recycle stream having a liquid and a gas phase into a
reactor such that the weight percent of liquid based on the total
weight of the recycle stream is typically greater than about 2.0
weight percent".
The novel copolymers of the present invention may be suitably
prepared by the copolymerisation of ethylene with
alpha-olefins.
The preferred alpha-olefins are 1-butene, 1-hexene,
4-methyl-1-pentene and 1-octene. The most preferred alpha-olefin is
1-hexene.
Thus according to another aspect of the present invention there is
provided a method for the preparation of copolymers of ethylene and
alpha-olefins having (a) a density (D) in the range 0.895-0.910
g/cm.sup.3, (b) a melt index MI.sub.2 (2.16 kg, 190.degree. C.) in
the range of 0.01-6 g/10 min, (c) a Compositional Distribution
Branch Index (CDBI) in the range 55-85%, and (d) a sealing
initiation temperature (SIT) and density (D) satisfying the
relationship SIT.ltoreq.(A.times.D)-B wherein A is 800.degree.
C..times.cm.sup.3/g and B is 650.degree. C. wherein the SIT
(.degree. C.) is determined on a 70 .mu.m film at 0.5N/15 mm and D
is in units of g/cm.sup.3, said method comprising copolymerising
ethylene and said alpha olefins in the presence of a catalyst
system as hereinbefore described.
Preferred copolymers have a density (D) in the range 0.900 to 0.910
g/cm.sup.3, and most preferably in the range 0.901 to 0.907
g/cm.sup.3.
Preferred copolymers have a melt index in the range 0.05 to 5 g/10
min and most preferably in the range 1.2 to 1.6 g/10 min.
The preferred relationship between the sealing initiation
temperature (SIT) and density (D) is when A is 1200.degree.
C..times.cm.sup.3/g and B is 1014.degree. C. and most preferred
when A is 1700.degree. C..times.cm.sup.3/g and B is 1469.degree.
C.
The novel copolymers are particularly suitable for the production
of films using traditional methods well known in the art.
Thus according to another aspect of the present invention there is
provided a film comprising a copolymer of ethylene and an
alpha-olefin having (a) a density (D) in the range 0.895-0.910
g/cm.sup.3, (b) a melt index MI.sub.2 (2.16 kg, 190.degree. C.) in
the range of 0.01-6 g/10 min, (c) a Compositional Distribution
Branch Index (CDBI) in the range 55-85%, and (d) a sealing
initiation temperature (SIT) and density (D) satisfying the
relationship SIT.ltoreq.(A.times.D)-B wherein A is 800.degree.
C..times.cm.sup.3/g and B is 650.degree. C. wherein the SIT
(.degree. C.) is determined on a 70 .mu.m film at 0.5N/15 mm and D
is in units of g/cm.sup.3.
Preferred copolymers have a density (D) in the range 0.900 to 0.910
g/cm.sup.3, and most preferably in the range 0.901 to 0.907
g/cm.sup.3.
Preferred copolymers have a melt index in the range 0.05 to 5 g/10
min and most preferably in the range 1.2 to 1.6 g/10 min.
The preferred relationship between the sealing initiation
temperature (SIT) and density (D) is when A is 1200.degree.
C..times.cm.sup.3/g and B is 1014.degree. C. and most preferred
when A is 1700.degree. C..times.cm.sup.3/g and B is 1469.degree.
C.
The films of the present invention also exhibit improved hot tack
strength at low sealing temperature. The temperature at which the
hot tack strength is equal to 3 N is .ltoreq.95.degree. C.,
preferably .ltoreq.92.degree. C. and most preferably
.ltoreq.90.degree. C.
The polymer powder prepared from the copolymers of the present
invention show unexpected excellent flowability resulting in
advantages downstream from the reactor. The flowability may be
expressed in terms of the compressability of the polymer powders.
The compressability is a qualitative index of the powder
flowability downstream of the reactor and may be used to highlight
potential issues or problems that may occur in the powder flow.
Polymer powders showing compressabilities of about 20% may give
rise to significant problems downstream of the reactor and hence it
is desirable to maintain compressabilities below 18% and preferably
below 16%.
The polymer powder prepared from the copolymers of the invention
show low powder compressability unexpected for their low
densities
Accordingly the copolymers of the present invention exhibit a
powder compressability (C) as follows: % C<(-A.times.D)+B
wherein D is the density in units of kg/m.sup.3, and A is 1 and B
is 928.
Preferably A is 0.75 and B is 698 and most preferably A is 0.5 and
B is 468.
The films may suitably comprise a multilayer film comprising a
number of layers at least one of which comprises copolymers as
hereinbefore described.
The films may suitably be used as sealing layers for packaging
applications.
The present invention will now be further illustrated with
reference to the following examples:
EXAMPLES 1 AND 2
Catalyst Preparation
Treatment of Silica with Triethylaluminium
Under continuous agitation, 2172 L of isohexane and 434.5 kg of
silica SY2408 (available from W.R. Grace), were added to a reactor.
(The silica was previously calcined under nitrogen to reach a level
of hydroxyl groups of 1.5 mol/kg). 21.3 kg of a Statsafe 2500
(supplied by Innospec) solution in iso-hexane (2 g/L) was then
added and the mixture was stirred for 15 minutes. 721 kg of a 12 wt
% triethylaluminium (TEA) solution in isohexane was then slowly
added over 1 hour and the mixture was stirred for 1 hour further at
30.degree. C.
The slurry was filtered and thoroughly washed with isohexane before
being transferred to a dryer. 21.3 kg of Statsafe2500 in isohexane
(2 g/l) was added and the mixture was finally dried at 60.degree.
C. under vacuum.
The aluminium content of the solid was 3.62 wt %.
Preparation of Catalyst Component (1)
To 404.6 kg of a 10.6 wt % solution of
[NH)Me(C.sub.18-22H.sub.37-45).sub.2][B(C.sub.6F.sub.5).sub.3(p-OHC.sub.6-
H.sub.4)] in toluene were added over 15 minutes 35.7 kg of 12 wt %
TEA solution in isohexane. The mixture was further stirred for 15
minutes to yield a solution of catalyst component 1.
Preparation of a Mixture of
(C.sub.5Me.sub.4SiMe.sub.2N.sup.tBu)Ti(.eta..sup.4-1,3-Pentadiene)
with 1-Hexene
130.2 kg of a 9.87 wt % solution of
(C.sub.5Me.sub.4SiMe.sub.2N.sup.tBu)Ti(.eta..sup.4-1,3-pentadiene)
in heptane and 83 kg of 1-hexene were mixed together during 15
min.
Preparation of the Supported Catalyst
483.5 kg of the above prepared silica/TEA was introduced into a
reactor. The above prepared solution of catalyst component 1 was
fed to the reactor over 60 min and the mixture was then stirred for
further 30 minutes.
The contents of the reactor was then cooled to 15.degree. C. and
the above prepared solution of
(C.sub.5Me.sub.4SiMe.sub.2N.sup.tBu)Ti(.eta..sup.4-1,3-pentadiene)
and 1-hexene was fed over a period of 30 minutes, and then the
mixture was further stirred for 40 minutes.
12.8 kg of a Statsafe2500 solution in isohexane (200 g/l) was then
added and the mixture was dried at 60.degree. C. during 13 hours
until the residual solvent content in the catalyst was <1 wt %.
Analysis of the resulting free flowing powder showed the titanium
content to be 56 .mu.mol/g, the boron content to be 59 .mu.mol/g
and the aluminium content to be 2.9 wt %.
EXAMPLE 3 (COMPARATIVE)
Example 3 is an ethylene-octene copolymer commercialized by
Borealis under the reference QUEO 0201 produced using a metallocene
catalyst in a solution polymerisation process.
EXAMPLE 4 (COMPARATIVE)
Example 4 is an ethylene-octene copolymer commercialized by
Borealis under the reference QUEO 1001 produced using a metallocene
catalyst in a solution polymerisation process.
EXAMPLE 5 (COMPARATIVE)
Example 5 is an ethylene-hexene copolymer of density 0.918
g/cm.sup.3 manufactured according to the teaching parameters in the
aforementioned WO 2008/074689.
Polymerization
Polymerizations using the catalysts prepared in examples 1 and 2
were carried out continuously using a fluidized bed gas phase
reactor of 74 cm diameter, with a vertical cylindrical section of 7
m. Polymerization conditions used are shown in Table 1 as
follows
TABLE-US-00001 TABLE 1 Example 1 2 Production Rate Kg/h 187 188
Reaction temp (.degree. C.) 70 72 Reaction pressure (barg) 20 20 C2
partial pressure (bar) 11.6 12.3 H2 to C2 pressure ratio (mol/mol)
0.0038 0.0036 C6 partial pressure (bar) 0.069 0.067 C5 partial
pressure (bar) 1.6 1.7 Residence time (hrs) 3.3 4 Condensation rate
(wt %) 0 0
Product Characteristics
The product characteristics are shown below in Table 2.
TABLE-US-00002 TABLE 2 Example 1 Example 2 CE3 CE4 CE5 Density
(g/cm.sup.3) 0.9013 0.9063 0.9007 0.9097 0.918 MI.sub.2 (2.16
kg/190.degree. C.) 1.13 1.15 1.26 1.1 1.3 CDBI (%) 69.8 83.3 88.5
94.0 68.2 (A .times. D) - B* 71.04 75.04 70.56 77.76 84.4 SIT at
0.5N (.degree. C.) 60 71 72 79 92 Mn (kDa) 32.2 30.4 30.5 27.2 29.0
Mw (kDa) 117.3 115.2 92.6 89.6 117 Mz (kDa) 265.3 261.2 188.3 199.0
276 Mw/Mn 3.6 3.8 3.0 3.3 3.8 Mz/Mn 2.3 2.3 2.0 2.2 2.4 Peak
melting temp .degree. C. 86.5/114.7 91.9/114.9 95.4 104.8
102/117.7/121.4 CSF55 (%) 17.4 11.4 11.1 3.9 0.8 Maximum Hot tack
10.9 11.8 10.0 9.8 11.3 strength (N) Temperature with 87 89 99 107
124 Hot tack strength of 3N (.degree. C.) Powder compressability
(%) 14.8 10.2 *A = 800 and B = 650.
Melt index (190/2.16) was measured according to ISO 1133. Density
was measured using a density column according to ISO 1872/1 method
except that the melt index extrudates were not annealed but left to
cool on a sheet of polymeric material for 30 minutes. Gel
Permeation Chromatography Analysis for Molecular Weight
Distribution Determination Apparent molecular weight distribution
and associated averages, uncorrected for long chain branching, were
determined by Gel Permeation Chromatography using a GPC IR device
from Polymer ChAR (, with 3 TSK GMHh r-H (S) columns from TOSOH
CORPORATION and a IR5 detector a infra-red detector supplied by
Polymer ChAR. The solvent used was 1,2,4 Trichlorobenzene at
160.degree. C., which is stabilised with BHT, of 0.1 g/litre
concentrationer. Polymer solutions of 1.0 g/litre concentration
were prepared at 160.degree. C. for one hour with stirring only at
the last 30 minutes. The nominal injection volume was set at 200
.mu.l and the nominal flow rate was 1 ml/min.
A relative calibration was constructed using 13 narrow molecular
weight linear polystyrene standards:
TABLE-US-00003 PS Standard Molecular Weight 1 3900 000 2 1 950 000
3 1 160 000 4 9952 600 5 488 400 6 195 900 7 70 950 8 49 170 9 30
230 10 19 760 11 10 680 12 1 930
The elution volume, V, was recorded for each PS standards. The PS
molecular weight was then converted to PE equivalent using the
following Mark Houwink parameters k.sub.ps=1.75.times.10.sup.-4,
.alpha..sub.ps=0.67, k.sub.pe=5.1.times.10.sup.-4,
.alpha..sub.pe=0.706. The calibration curve Mw.sub.PE=f(V) was then
fitted with a first order linear equation. Number average molecular
weight (Mn), weight average molecular weight (Mw), z-average
molecular weight (Mz) are computed using the formula given the text
book "Properties of Polymers correlation with chemical structure"
by D. W. Van Krevelen, Elsevier Publishing Company, Amsterdam,
1972. All the calculations are done with GPC one software from
Polymer Char.
The very low molecular weight fractions (below 600 Daltons) were
routinely excluded in the calculation of number average molecular
weight, Mn, and hence the polymer polydispersity, Mw/Mn, in order
to improve integration at the low end of the molecular weight
curve, leading to a better reproducibility and repeatability in the
extraction and calculation these parameters.
Peak Melting temperature was determined by differential scanning
calorimetry using a Perkin Elmer Diamond model following the
methodology outlined in ASTM D3417 except that the first heating
was carried out at 20.degree. C./mn. The peak temperature is taken
as the temperature correspond to a maximum heat flow observed
during the second heating of the polymer at 10.degree. C./mn. In
case of several peaks during melting are observed, for each maximum
a peak melting temperature is recorded. Composition distribution
breadth index ("CDBI") is defined as the weight percent of the
copolymer molecules having a comonomer content within 50% of the
median total molar comonomer content. The CDBI is determined by
Temperature Rising Elution Fraction (TREF). TREF experiments
analysis was conducted in a commercial CRYSTAF model 200 instrument
from Polymer Char. Approximately 60 mg of polymer is dissolved at
150.degree. C. for 60 minutes in 25 mL of 1,2,4 Trichlorobenzene
stabilised with BHT, of 0.1 g/litre. 1.8 ml of the solution is then
transferred into the column and allowed to equilibrate for
approximately 45 minutes at 95.degree. C. The polymer solution is
then cooled to 35.degree. C. using a cooling rate of 0.5.degree.
C./min. After 20 mn stabilization, TCB is eluted through the column
at 0.5 ml/mn at 35.degree. C. The polymer concentration is measured
at the column outlet by an Infra Red detector. After the soluble
species is fully eluted, the column temperature is increased at
1.degree. C./mn until 120.degree. C. After completion of the
elution, CDBI is calculated from the elution profile.
Crystallizable Species Fraction below 55.degree. C. ("CSF55") is
defined as the weight percentage of copolymers eluted between 35
and 55.degree. C. over the eluted amount between 35 to 120.degree.
C. CSF55 is determined by TREF under the same conditions used for
CDBI determination. Powder Compressability
The compressibility factor C (%) was determined on a Flow Rate
Indicizer supplied by Johanson Innovations Inc, 102 Cross Street
Suite #110 San Luis Obispo, Calif. 93401. The Flow Rate Indicizer
equipment enables to assess qualitatively the powder flowability
due to the compressibility factor being defined as:
.times..times. ##EQU00001## where: FDI: Feed Density Index, which
is the powder bulk density at silo feed, i.e. close to Settled Bulk
Density.
BDI: Bin Density Index, which the bulk density of the powder
submitted to 500 standard impacts according to NFT 51-042.
Both Density Indexes were determined at 60.degree. C.
Film Characteristics
The films were extruded on a blown film line under the following
conditions
TABLE-US-00004 Supplier Dr Collin Model Extruder M type 180/600
Screw diameter 45 mm Screw L/D Ratio 25D Die diameter 100 mm Die
gap 1.2 mm Temperature Profile
190/200/205/210/215/215/220/220.degree. C. Output 15 kg/h Blow-up
ratio 2:1 Frostline height 330 mm Film thickness 70 .mu.m
The sealing initiation temperature (SIT) was calculated from the
sealing strength--sealing temperature curve for a sealing strength
of 0.5 N/15 mm. Seal strength is determined by cutting two
superimposed film specimen of 130 mm.times.150 mm.times.70 .mu.m in
transversal direction (TD) using the film cutting template. To
avoid the film sticking to the hot plate, the test specimen are
placed between two layers of Mylar film (25 .mu.m) then put between
the hot jaws of the sealing machine from OTTO BRUGGER with the
transversal direction of the film along the length of the jaws. The
films are sealing at the set temperatures corresponding to
10.degree. C. step between 50 and 140.degree. C. The pressure is 2
bars and sealing time is 0.5 s. Three 15 mm width strips are cut in
the Machine Direction and conditioned for 24 h at 23.degree. C. at
50% relative humidity. The specimens are peeled in a tensile
machine at 200 mm/mn with a initial distance between the two jaws
of 50 mm. The sealing strength is recorded at specimen breakage and
average across the three specimens.
The temperature with a hottack strength of 3N and maximum hottack
strength were calculated from the hottack strength--sealing
temperature curve and corresponds to the lowest sealing temperature
for which the hottack strength is superior or equal to 3 N and
highest strength recorded between 50 to 140.degree. C.
respectively.
The hottack strength is determined with a Topwave Hot Tack Tester
on 25 mm-width film specimens in the TD direction. The film
specimens are back-taped with a thermo-resistant adhesive tape
(reference 51588 from VAN ROLL ISOLA). The Hot Tack Tester settings
were: Seal Pressure: 0.14 N/mm2 Seal Time: 0.4 sec Cool Time: 0.3
sec Peel Speed: 150 mm/sec Force Range: 100N Seal temperature:
80-90-95-100-105-120-125-130-140-150-160-170-180.degree.
* * * * *